Method of controlling a potential difference between a stencil mask and a substrate of semiconductor device

ABSTRACT

A method of manufacturing a semiconductor device is disclosed, which comprises setting a stencil mask above a substrate to be processed in confronting to the substrate, the stencil mask having an opening, and irradiating the substrate with charged particles through the opening of the stencil mask, while adjusting a potential difference between the stencil mask and the substrate depending on a value of a current flowing between the substrate and the stencil mask.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of the priorityfrom the prior Japanese Patent Application No. 2002-375979, filed Dec.26, 2002, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing asemiconductor device using, for example, a stencil mask as a transfermask and an apparatus for manufacturing the semiconductor device.

2. Description of the Related Art

There has been known a method in which in semiconductor devicemanufacturing process, a stencil mask having a predetermined pattern isset above a substrate to be processed at a predetermined distance andcharged particles such as electrons or ions are projected onto thesubstrate through openings defining the pattern of the stencil mask. Inthe method, charged particles (ion beam) such as ions accelerated from aparticle source by a predetermined energy pass through a scanner and amagnet to be formulated into a patterned ion beam. The patterned ionbeam is projected onto the substrate through the openings formed in thestencil mask. The substrate to be processed mentioned here is asemiconductor substrate, on the surface of which a semiconductor deviceis to be formed or has been formed, not shown.

There is a disadvantage that, when a substrate is processed using thecharged particles, residue charges are accumulated on the substrate sothat the semi-conductor device formed on the substrate may be destroyedby being charged due to the accumulated charges. A conventional methodis known to overcome this disadvantage (Jpn. Pat. Appln. KOKAIPublication No. 9-283411, see page 4). In this method, secondaryelectrons or plasma electrons are generated to neutralize theaccumulated charges, thus preventing the destruction of a substrate dueto the accumulated charges.

Jpn. Pat. Appln. KOKAI Publication No. 2002-203806 FIGS. 29 and 35)discloses a method of controlling the amount of charges accumulated on asubstrate to be processed. In the method, a distance and a potentialdifference between a stencil mask and the substrate to control theamount of charges accumulated on the substrate. The controlling of theamount of charges is carried out by providing a power supply between thestencil mask and the substrate, or by providing a power supply betweenthe stencil mask and the ground and also another power supply betweenthe substrate and ground.

However, neutralizing the accumulated charges by generating secondaryelectrons or plasma electrons is sensitive to the amount of charges onthe substrate and the stencil mask, the amount of energy on chargedparticles, degree of vacuum in the apparatus, etc., and the amount ofneutralized charges greatly changes depending on these factors. As aresult, with the method of neutralizing the accumulated charges bygenerating secondary electrons or plasma electrons, the neutralizedcharge amount may be insufficient or an excessive amount of electronsmay be supplied to cause negative charging, which possibly destroy thesemiconductor devices. Further, the charge neutralizing mechanism, whichgenerates the secondary electrons or plasma electrons, is complicated instructure.

On the other hand, according to the method of controlling the amount ofthe charges accumulated on the substrate by changing a distance and apotential difference between the stencil mask and the substrate, yieldis improved. However, it is necessary to set up the distance and thepotential difference between the stencil and the substrate before an ionimplantation process is carried out. There is no problem if theirradiation condition of the charged particles is stable and the stateof the apparatus is stable during the processing. However, if theapparatus is unstable, and the irradiation amount (current amount) ofthe charged particles per unit time changes during the processing, theneutralized charge amount may be insufficient, or an excessive amount ofelectrons may be supplied to cause negative charging, which leas to apossible destruction of the semiconductor devices.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided amethod of manufacturing a semiconductor device comprising:

setting a stencil mask above a substrate to be processed in confrontingto the substrate, the stencil mask having an opening; and

irradiating the substrate with charged particles through the opening ofthe stencil mask, while adjusting a potential difference between thestencil mask and the substrate depending on a value of a current flowingbetween the substrate and the stencil mask.

According to another aspect of the present invention, there is provideda method of manufacturing a semiconductor device comprising:

setting a stencil mask above a substrate to be processed in confrontingwith the substrate, the stencil mask having an opening; and

irradiating the substrate with charged particles through the opening ofthe stencil mask, while adjusting a potential difference between thestencil mask and the substrate depending on a ratio between a value of acurrent flowing in the substrate and a value of a current flowing in thestencil mask.

According to a further aspect of the present invention, there isprovided a manufacturing apparatus of a semiconductor device,comprising:

a stencil mask set above a substrate to be processed in confronting tothe substrate, the stencil mask having an opening;

a particle source which irradiates the substrate to be processed withcharged particles through the opening of the stencil mask;

a first power supply which is connected to the stencil mask and changesa potential of the stencil mask; and

a first ammeter connected to the substrate to be processed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagram showing part of a semiconductor device manufacturingapparatus according to a first embodiment of the present invention;

FIG. 2 is a diagram showing part of a semiconductor device manufacturingapparatus according to a second embodiment of the present invention; and

FIG. 3 is a diagram showing part of a semiconductor device manufacturingapparatus according to a third embodiment of the second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIRST EMBODIMENT

FIG. 1 shows a semiconductor manufacturing apparatus according to afirst embodiment of the present invention.

In a semiconductor manufacturing process, a stencil mask 11 having apredetermined pattern formed by openings formed in the stencil mask isset above a substrate 12 to be processed at a distance. Chargedparticles 13 (ion beam) such as ion accelerated by an energy passthrough a scanner and a magnet are formulated into a pattern of chargedparticles. The patterned ion beam 13 is irradiated onto the substrate 12through the openings formed in the stencil mask. The substrate 12 to beprocessed mentioned here is a semiconductor substrate, in which asemiconductor device is to be formed or has been formed, not shown.

The stencil mask 11 is connected to a power supply 14 which is alsoconnected to ground. Thus, a potential of the stencil mask 11 can becontrolled, with an outer wall of the apparatus or ground as a referencepotential. The substrate 12 is connected to the outer wall of theapparatus or ground through an ammeter 15. Thus, current flowing fromthe substrate can be measured by the ammeter 15.

When the irradiation amount of the ion beam 13 is not changed in asemiconductor manufacturing process such as an ion implantation process,that is, when the quantity of the charged particles applied to thesubstrate 12 is constant, a current I₁ measured by the ammeter 15 isalso constant. That is, an appropriate current value for processingcondition of processing the substrate 12 exists and the appropriatecurrent value is usually constant. Although most preferably, theconstant value of the current I₁ is 0(A), it is not restricted to thisvalue but may be other constant value than 0(A).

If electrical balance between the stencil mask 11 and the substrate 12is get out due to factor variations of the apparatus so that theneutralizing effect is lowered, excessive positive charges may begin tobe accumulated on the surface of the substrate 12. The excessivepositive charges accumulated on the surface of the substrate 12 flow tothe outer wall of the apparatus so that the current I₁ increases. Thus,according to this embodiment, the current I₁ flowing to the substrate 12is measured and if the current I₁ becomes larger than the appropriatecurrent value for some reason during ion implantation, the positivecharges which begin to be accumulated on the substrate 12 can beneutralized by lowering a potential of the stencil mask 11 by the powersupply 14. If the potential of the stencil mask 11 is lowered too muchwhen the potential of the stencil mask 11 is adjusted, negative chargesare then accumulated on the surface of the substrate 12, and a currentI₂ becomes smaller than an appropriate current value. The current I₂ isa current flowing through the power supply 14. In this case, thenegative charges which begin to be accumulated on the substrate 12 canbe neutralized by increasing the potential of the stencil mask 11 by thepower supply 14.

Thus, according to this embodiment, even if the neutralizing conditionchanges due to an instable state of the apparatus, in the semiconductormanufacturing process using the charged particles such as ionimplantation process, the potential of the stencil mask can be changedfollowing the state of the apparatus. Consequently, the possibility thatthe semiconductor device may be destroyed due to the charges accumulatedon the substrate is reduced, thus yield is improved.

SECOND EMBODIMENT

FIG. 2 shows a semiconductor manufacturing apparatus according to asecond embodiment of the present invention. Reference numeralscorresponding to those used in FIG. 1 are attached to the correspondingcomponents, and description thereof is omitted.

In a semiconductor manufacturing process, a stencil mask 21 having apredetermined pattern formed by openings formed in the stencil mask isset above a substrate 22 to be processed at a distance. Chargedparticles 23 (ion beam) such as ion accelerated by an energy passthrough a scanner and a magnet are formulated into a pattern of chargedparticles. The patterned ion beam 23 is irradiated onto the substrate 22through the openings formed in the stencil mask. The substrate 22 to beprocessed mentioned here is a semiconductor substrate, in which asemiconductor device has been formed, not shown.

The stencil mask 21 is connected to a power supply 24 which is also isconnected to ground (i.e. an outer wall of the apparatus) through anammeter 25. Thus, a potential of the stencil mask 21 can be controlled,with the outer wall of the apparatus or ground as a reference potential.Further, a current flowing from the stencil mask 21 can be measured bythe ammeter 25. The substrate 22 is connected to ground (i.e. an outerwall of the apparatus) through an ammeter 26. Thus, a current flowingfrom the substrate can be measured by the ammeter 26.

When the irradiation amount of the ion beam 23 is not changed in asemiconductor manufacturing process such as an ion implantation process,that is, when the quantity of the charged particles applied to thesubstrate 22 is constant, a current I₁ measured by the ammeter 25 isalso constant. That is, an appropriate current value for processingcondition of processing the substrate 22 exists and that the appropriatecurrent value is usually constant. Although most preferably, theconstant value of the current I₁ is 0(A), it is not restricted to thisvalue but may be other constant value than 0(A).

However, if the irradiation amount of the ion beam 23 per unit timechanges with time in the semiconductor manufacturing process such as anion implantation process, the quantity of the charged particles appliedto the substrate 22 per unit time also changes, so that the current I₁measured with the ammeter 26 also changes. On the other hand, the ratioof the current I₁ flowing from the substrate 22 with respect to thecurrent I₂ flowing from the stencil mask 21, that is, a current ratioI₁/I₂, is constant, since the neutralizing effect is maintained if theelectrical balance between a stencil mask 21 and the substrate 22 isstabilized. That is, an appropriate current ratio depending on theprocessing condition of processing the substrate 22 exists, and usuallythat value is constant.

If electrical balance between the stencil mask 21 and the substrate 22is get out due to factor variations of the apparatus so that theneutralizing effect is lowered, excessive positive charges may begin tobe accumulated on the surface of the substrate 22. If excessive positivecharges begin to be accumulated on the surface of the substrate 22, theratio of the current I₁ flowing from the substrate 22 with respect tothe current I₂ flowing from the stencil mask 21, that is, the currentratio I₁/I₂ is increased. Then, according to this embodiment, thecurrent ratio I₁/I₂ is measured and if the current ratio I₁/I₂ becomeslarger than its appropriate current ratio for some reason in the ionimplantation process, the positive charges which begin to be accumulatedon the substrate 22 can be neutralized by lowering the potential of thestencil mask 21 through a power supply 24. If the potential is loweredtoo much when the potential of the stencil mask 21 is adjusted, negativecharges are accumulated on the surface of the substrate 22, and thecurrent ratio I₁/I₂ becomes smaller than the appropriate current ratio.In this case, the negative charges which begin to be accumulated on thesubstrate 22 can be neutralized by lowering the potential of the stencilmask 21 by the power supply 24.

Thus, according to this embodiment, even if the irradiation amount ofthe ion beam changes with time in the semiconductor manufacturingprocess using the charged particles such as an ion implantation process,yield can be improved by reducing the possibility that the semiconductordevice may be destroyed due to the charges accumulated on the substrate.

THIRD EMBODIMENT

FIG. 3 shows a semiconductor manufacturing apparatus according to athird embodiment of the present invention. Reference numeralscorresponding to those used in FIG. 1 are attached to the correspondingcomponents, and description thereof is omitted.

In a semiconductor manufacturing process, a stencil mask 31 having apredetermined pattern formed by openings formed in the stencil mask isset above a substrate 32 to be processed at a distance. Chargedparticles 33 (ion beam) such as ion accelerated by an energy passthrough a scanner and a magnet are formulated into a pattern of chargedparticles. The patterned ion beam 33 is irradiated onto the substrate 32through the openings formed in the stencil mask. The substrate 32 to beprocessed mentioned here is a semiconductor substrate, in which asemiconductor device has been formed, not shown.

The stencil mask 31 is connected to a power supply 34 which is also isconnected to ground (i.e. an outer wall of the apparatus) through anammeter 35. Thus, a potential of the stencil mask 31 can be controlled,with the outer wall of the apparatus or ground as a reference potential.Further, a current flowing from the stencil mask 31 can be measured bythe ammeter 35. The substrate 32 is connected to a power supply 36 whichis also is connected to ground (i.e. an outer wall of the apparatus)through an ammeter 37. Thus, a potential of the substrate 32 can becontrolled, with the outer wall of the apparatus or ground as areference potential. Further, a current flowing from the substrate 32can be measured by the ammeter 37.

When the irradiation amount of the ion beam 33 is not changed in asemiconductor manufacturing process such as an ion implantation process,that is, when the quantity of the charged particles applied to thesubstrate 32 is constant, a current I₁ measured by the ammeter 35 isalso constant. That is, an appropriate current value for processingcondition of processing the substrate 32 exists and the appropriatecurrent value is usually constant. Although most preferably, theconstant value of the current I₁ is 0(A), it is not restricted to thisvalue but may be other constant value than 0(A).

However, if the irradiation amount of the ion beam 33 per unit timechanges with time in the semiconductor manufacturing process such as anion implantation process, the quantity of the charged particles appliedto the substrate 32 per unit time also changes, so that the current I₁measured with the ammeter 36 also changes. On the other hand, the ratioof the current I₁ flowing from the substrate 32 with respect to thecurrent I₂ flowing from the stencil mask 31, that is, a current ratioI₁/I₂ is constant, since the neutralizing effect is maintained if theelectrical balance between a stencil mask 31 and the substrate 32 isstabilized. That is, an appropriate current ratio depending on theprocessing condition of processing the substrate 32 exists, and usuallythat value is constant.

If electrical balance between the stencil mask 31 and the substrate 32is get out due to factor variations of the apparatus so that theneutralizing effect is lowered, excessive positive charges may begin tobe accumulated on the surface of the substrate 32. If excessive positivecharges begin to be accumulated on the surface of the substrate 32, theratio of the current I₁ flowing from the substrate 32 with respect tothe current I₂ flowing from the stencil mask 31, that is, the currentratio I₁/I₂ is increased. Then, according to this embodiment, thecurrent ratio I₁/I₂ is measured and if the current ratio I₁/I₂ becomeslarger than its appropriate current ratio for some reason in the ionimplantation process, the positive charges which begin to be accumulatedon the substrate 32 can be neutralized by decreasing the potentialdifference between the stencil mask 31 and the substrate 32 throughpower supplies 34, 36. If the potential difference is lowered too muchwhen the potential difference between the stencil mask 31 and thesubstrate 32 is adjusted, negative charges are then accumulated on thesurface of the substrate 32, and the current ratio I₁/I₂ becomes smallerthan the appropriate current ratio.

According to the present embodiment, the negative charges which begin tobe accumulated on the substrate 32 can be neutralized by adjusting thepower supplies 34, 36 to thereby increase the potential differencebetween the stencil mask 31 and the substrate 32. At this time,considering an influence upon the semi-conductor device, it ispreferable that the power supply 36 connected to the substrate 32 isused as a supplement of the power supply 34. An optimum neutralizationcan be attained since the potentials of the stencil mask 31 and thesubstrate 32 can be independently adjusted by using the power supplies34, 36 connected to the stencil mask 31 and the substrate 32. Thus,according to the present embodiment also, the possibility that thesemiconductor device may be destroyed due to the charges accumulated onthe substrate is lowered and thus yield can be improved, even if theirradiation amount of the ion beam changes with time in thesemiconductor manufacturing process using the charged particles such asion implantation process.

As described in detail above, according to the embodiments of thepresent invention, the possibility that the semiconductor device may bedestroyed by the charges accumulated on the substrate in thesemi-conductor manufacturing process using the charged particles such asthe ion implantation process can be decreased, thereby improving theyield.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A method of manufacturing a semiconductor device comprising: settinga stencil mask at a distance above a substrate to be processed, thestencil mask having an opening defining a cross-sectional area throughwhich charged particles are allowed to pass; and irradiating thesubstrate with charged particles through the opening of the stencilmask, while adjusting a potential difference between the stencil maskand the substrate depending on a value of a current flowing between thesubstrate and ground, so that the value of the current flowing betweenthe substrate and ground becomes a predetermined value.
 2. A method ofmanufacturing a semiconductor device, according to claim 1, whereinadjusting the potential difference includes changing a potential of thestencil mask with ground as a reference potential, by using a firstpower supply provided between the stencil mask and ground.
 3. A methodof manufacturing a semiconductor device, according to claim 1, whereinadjusting the potential difference includes changing a potentialdifference between the stencil mask and the substrate, by using a firstpower supply provided between the stencil mask and ground and a secondpower supply provided between the substrate and ground.
 4. Asemiconductor device manufacturing method according to claim 1, whereinadjusting the potential difference includes decreasing a potential ofthe stencil mask when the current flows from the substrate to ground andthe value of the current flowing from the substrate to ground is largerthan the predetermined value, and increasing the potential of thestencil mask when the current flows from the substrate to ground and thevalue of the current flowing from the substrate to ground is smallerthan the predetermined value.
 5. A method of manufacturing asemiconductor device comprising: setting a stencil mask at a distanceabove a substrate to be processed, the stencil mask having an openingdefining a cross-sectional area through which charged particles areallowed to pass; and irradiating the substrate with charged particlesthrough the opening of the stencil mask, while adjusting a potentialdifference between the stencil mask and the substrate depending on aratio between a value of a current flowing between the substrate andground and a value of a current flowing between the stencil mask andground, so that the ratio of the currents becomes a predetermined value.6. A method of manufacturing a semiconductor device, according to claim5, wherein adjusting the potential difference includes changing apotential of the stencil mask with ground as a reference potential, byusing a first power supply provided between the stencil mask and ground.7. A method of manufacturing a semiconductor device, according to claim5, wherein adjusting the potential difference includes changing apotential difference between the stencil mask and the substrate, byusing a first power supply provided between the stencil mask and groundand a second power supply provided between the substrate and ground. 8.A semiconductor device manufacturing method according to claim 5,wherein adjusting the potential difference includes decreasing apotential of the stencil mask when the current flows from the substrateto ground and the ratio of the values of the currents is larger than thepredetermined value, and increasing the potential of the stencil maskwhen the current flows from the substrate to ground and the ratio of thevalues of the currents is smaller than the predetermined value.